TEST STRIP, OPA 28 HI-LVL DISINFECTANT (50/BT 2BT/ MGM16 McKesson OPA/28 Test Strips To verify the efficacy of McKesson OPA/28 Solution, user should test for the minimum effective concentration (MEC) prior to each use. 3 second dip time 90 seconds read time Large, easy-to-read indicator pad. Definitive color identification comparison chart on each bottle. 18-month shelf life (unopened bottle), 6-month shelf life from date of opening. Not Made with Natural Rubber Latex. Packaged: 50 Strips Per Bottle, 2 Bottles Per Case